Treatment of magnetic alloys and products resulting therefrom



alloys to increase the perature of about 2000 'creasin Patented Mar. 14,1933 CLARENCE GEORGE IBIEBEB, 0F REMINGTON,

NTf-OFEIQE INTERNATIONAL NICKEL COMPANY, 1110., OF NEW YORK, 11'. 21-, ACORPORATION OF DELAWARE rnmmnur on'imemc rumors AND rnonuc'rs nrsun'rmeEmma No Drawing.

This invention relates to a process of treating magnetic alloys-and moreparticularly'to a method of heat treating alloys of the nic eliron typeto increase the permeability thereof, and to the new products resultingtherefrom.

An object of the resent invention is to provide a method 0 heat tre'atinmagnetic A- further object 0' the invention is to provide a simple and1practical method of heat;

treating magnetic a oys of the nickel-iron type which can be carried outsatisfactorily on an-industrial scale.

It is, another object of the invention to provide a method of heattreating magneticalloys particularly permallo like so as to increase thepermeabi ity thereof several times greater than that of the commercialalloys on the market while only inthe cost of production a practicallyne ligi 'le amount.

ther objects bf the invention will become clear from the description ofaspecific procedure for carrying the invention into practice.

A magnetic alloy of the iron-nickel type such as permalloy is producedin the usual way. After production, the alloy is prefer ably fabricatedinto the form. in which it is to be used. For example, the alloy may berolled into sheets. Care should be exercised at this stage of theoperation to clean the fabricated magnetic alloy and free the same fromgrease before annealing.

The magnetic alloy of the permalloy. type is subjected to an initialsuper-annealing treatment in which a super-temperature is employed for aperiod of time scient to produce the new results of the presentinvention. In practice, it has been found that subjecting the magneticalloys to a super-tem- F. to about 2200 F. is satisfactory whenmaintained for a period. of time from about 4 hours to about 8 hours.Following this initial super-annealing treatment, the alloy ispreferably slowly cooled. By slow cooling is meant cooling at a rateslower than 1000 il per hour. lit should be noted that the initialsuper-annealing and ermeabihty thereof.

and the Application filed February 19, 1982. Serial No. 594,155. I

the slow cooling should be carried ,out' ina hydrogen orequlvalentatmosphere.

The cooled magnetic alloy is reheated in air to a temperature of about1000 F to about 1200 F. for a period of time of about wns'r vmonmn-ASSIGNOR no man.

10 minutes to about 20 minutes- The reheated magnetic alloy is thenrapidly cooled on a copper plate which initially has a temphere. Insteadof using a coppen plate, a moist cloth can beused for rapidly coolingthe'heated magnetic-material.

- The magnetic alloys produced by the foregoing procedure have beenfound to possess far greater permeability'than the same alloy whensubjected to the old conventional heat ""perature approximating that ofthe atmostreatment. On the average, it has been found that thepermeability of'the magnetic alloy subjected to the heat treatment ofthe present invention is at least two to three times greater than thepermeability ofthe same magnetic alloy when subjected to the heattreatment. At the same time, the cost of producing the greaterpermeability in the magnetic alloy is very slight and is practicallynegligible when compared with the selling price of the allo A specificexample will now be described of carrying the invention into practice onan industrial scale. It is to be noted, however, that theexample ismerely for illustrative purposes and for a better understanding of theinvention for those skilled in the art.

A magnetic alloy of the permalloy type composed'of about 78 76 nickeland about 21%% iron is cleaned and is free from grease. It is preferredto coat the sheets or the like of magnetic alloy with a refracoldconventional,

till

F. This super-anancetype of furnace. By maintaining the a sheets at thesuper-annealing temperature of 2000 F. for a period of about 4 hours,the new results of t e present invention may be obtained.

The sheets heated to the super-annealing temperature are slowly cooledin'the furnace preferably in a hydrogen atmosphere. After subjected tothe foregoing procedure were found to give surprisingly highpermeability. These permeabilities were in each case at least threetimes greater than the permeabilities of the same alloy when subjectedto the old conventional heat treatment. The following table givesfigures which clearly illustrate the new results produced by the presentinvention.

Table Maximum permeabilitiea of nickel-iron alloy of permalloy typeBasic electric furnace melts Old heat treatment New heat Mel treatmentAcid electric furnace melts Old heat treatment New heat Melt treatmentAcid open hearth mella Old heat treatment New heat ,Melt treatment Y-auFrom the foregoing table, it will be appreciated'that the permeabilitiesgiven. for the magnetic alloys when subjected to the old conventionalheat treatments approximate those of the commercial magnetic alloys ofthe permalloy type now on the market. The figures given for the magneticalloys of the permalloy type show that the present invention producespermeabilities which are far in excess of those of old conventionalalloys. In eneral, the present invention ives permea ilities from abouttwo to a ve five times higher than those given by conventional heattreatments. The benefits to be enjoyed by the art from the presentinvention are" the present invention and the 1m roved magnetic alloywith super-permeabi ities can be that other alloys of nickel-ironcomposition will be greatly enhanced in their permeability by employingthe method of heat treatment herein. V

For instance, alloys having nickel from 65% to 80% and the balance ironshow' increases in permeability in accordance with the following tableMari mum permeability New heat treatment Old heat product is simple andneither difiicult nor lengthy in application, but it does permitproduction of a product having great value and permits this productionwith very little increase in cost, and practically no increase in costwhen considering the value of the new product. 7

It will also be observed that the present invention provides a processwherein permeabilities can be obtained which are in excess of 120,000;150,000; 200,000 and even 300,000. a

'Withnickel-iron alloys of the permalloy it will be observed from'thefirst table t pe t at a magnetic product can be produced of asuper-annealed nickel-iron alloy of the' permalloy type havingpermeabilities of at least 200,000.

It will alsoebe noted that the present invention provides a processwhich can be carried out on an industrial scale and which is capable ofproducing consistently and repeatedly magnetic alloys havingaermeability in excess of industrial magnetic products which haveheretofore been commercially available.-

Whatisclaimedis: 1. The. process of heattreating magnetic alloys of thenickel-ironjtype, which comprises subjecting such alloys to an initialsuper-annealing treatment, slowly cooling the super-annealed alloys in ahydrogen atmosphere, reheating the cooled alloys to about 1160 F. inair, and rapidlycooling I 0 about 4 hours at a temperature of about 2000netic alloys treated with conventional heat alloys of 3. An article ofmanufacture comprising an industrial magnetic product composed of anickel-iron alloy having a permeability in F., slowly coolingthesuper-annealed alloy in an atmosphere of hvdrogen, reheating thev cooledalloy to a temperature of about 1160 F. for about 15 minutes and thenrapidly cooling the thus reheated alloy on a copper plate havingatemperature approximating that of the atmosphere, whereby the magneticpermeability of the alloy is increased several times greater than thepermeability of mag treatments.

excess of at least 200,000.

4. An article of manufacture comprising an industrial magnetic productcomposed of a nickel-iron alloy having a permeability in excess of atleast 300,000.

5. An article of manufacture comprising an industrial magnetic productcomposed of an iron-nickel alloy which has been superannealed in ahydrogen atmosphere to impart a permeability in excess of 150000.

. 6. An article of manufacture comprising an industrial magnetic,product composed of aniron-nickel alloy which has been superannealed,slowly cooled in ahydrogen atmosphere, reheated in air to a hightempera: ture' and then rapidly cooled on a copper plate to impart apermeability to the product in excess of 150,000.

7. An article of manufacture comprising an industrial magnetic productcomposed of an iron-nickel alloy which has been superannealed at atemperature of about 2000 -F. for about 4 hours, slowly cooled in anatmosphere of hydrogemreheated in air to a tempcrature of about 1160 F.for about 15 min.- utes and rapidly cooled on a copper plate toimpartto,the product a permeability in excess of about 150,000.

8. An article of manufacture comprisin an industrialmagnetic productcomposed o an iron-nickel alloy nickel to about 80% nickel and thebalance iron, which has been super-annealed in a hydrogen atmosphere toimpart a permeability in excess of 150,000.

9. An article of manufacture comprisin an industrial magnetic productcomposed 0 an iron-nickel alloy consisting of about nickel to aboutnickel and the balance iron, which hasbeen super-annealed to impart a.ermeability in excess of 200,000.

10. an industrial magnetic product composed 0 an iron-nickel alloyconsisting of about 7 5% nickel to about 80% iron, which has beensuper-annealed to impart a permeability in excess of 300,000.

11 article of manufacture comprising,

nickel and the balance 11. In the art of heat treating magnetic alloysof the nickel-iron type, that improvement which comprises subjecting thenickeliron alloy to an initial super-annealing treatment in a hydrogenatmosphere substantially free from moisture and oxygen, slowly coolingthe super-annealed alloy in atmosphere substantially free from moistureand oxygen, reheating the cooled alloy to a temperature lower than saidsuper-anneal ing temperature and rapidly cooling the thus reheatedalloy, whereby the permeability of the allov is greatly increased.

12. The process of heat treating magnetic prises rolling a magneticiron-nickel alloy to, form .a sheet, treating said sheets to clean thesame and remove grease therefrom, coating the cleaned sheets with arefractory material ofthe group comprising magnesia and lime, saidrefractory material being free from sulfur, arranging thethus-coatedsheets in a stack, subjecting the stack to an initialsuper-annealing treatment for about several hours at a temperature ofabout 2000 F., slowly cooling the super-annealed alloy in a reducingatmosphere of dried gases, re-heating the cooled alloy to a temperatureof about 1160 F. for a relatively short time and then rapidly coolingthe thus reheated alloy, whereby the magnetic permeability of the alloyis greatly increased.

13. The process of heat treating magnetic alloys of the nickel-iron typewhich comprises subjecting such alloys -to an initial super-annealingtreatment in a reducing atmosphere containing hydrogen substantiallyfree from moisture, slowly cooling the super-annealed alloys in areduced atmosphere containing hydrogen substantially free from moisture,reheating the thus cooled alloys to a lower temperature than thesuperannealing temperature and rapidly cooling the thus reheated alloyswhereby the permeability of the alloys is greatly increased.

a hydrogen the nickel-iron type, which com- .In testimony whereof, Ihave hereunto set 1 my hand.

CLARENCE GEORGE BIEBER.

consisting of about 75% I

